Control apparatus for coating machines



Jan. 1, 1946. co E 2,392,229

CONTROL APPARATUS FOR COATING MACHINES Filed Jan. 26, 1943 3Sheets-Sheet 2 X R g e adore A [0% e22 INVENTOR,

BYJM/UM 1, 4 T. A. COHEN I CONTRO L APPARATUS FOR COATING MACHINES FiledJan. 26, 1943 3 Sheets-Sheet 3 o 77;cadareAL IM E TOR,

JM Z M Art aw m fi m W Y Patented Jan. 1, 1946 umrso STATES PATENTOFFICE Theodore A. Cohen, Chicago, 111., minor, by meme assignments, toWheelco Instruments Coarpany, Chicago, 11]., a corporation of lilino 7Application January 28, 1943, Serial No. 474,042 2: Claims. (01. 91-18)g This invention relates to control apparatus and more particularly to acontrol apparatus for antomatically controlling the admission andrecession of a liquid vehicle for fluorescent powder, commonly used forcoating the interior of fluorescent tubes, to and from the tubes.

One of the objects of my invention is to provide an apparatus forefficiently effecting and controlling the application of a liquidvehicle for fluorescent powders, such as above referred to, to theinterior of the tubes to sharply and effectively stop the rising of theliquid in the tubes when it has reached a predetermined point thereinand thereafter cause the recession of the liquid from the tubes tocomplete an application cycle. Other and further objects of my inventionwill be apparent as the same becomes better understood from anexamination of the specification and claims in conjunction with theaccompanying drawings wherein:

' Figure 1 represents a schematic view of anal!- paratus embodying myinvention;

Figure 2 is a diagrammatic view of the same;

Figure 3 is an enlarged, fragmentary, detail, elevational view, partlyin section and with parts removed, showing the portion 01' the apparatusfor mounting the fluorescent tubes to be coated by the powder carried bythe liquid vehicle to be introduced into and withdrawn from them Figure4 is a side elevation of same;

Figure 5 is an enlarged section at the line II! of Figure 3;

Ic'ligure 6 is a modified form of pick up clip, an

Figure 7 is a section taken at the line 1-1 of Figure 6.

Referring to the drawings more particularly, reference character Idesignates a liquid container carrying a liquid vehicle 2 forfluorescent powder commonly used for coating the interior of fluorescenttubes, such as tubes I8, "II, lab

4 and Itc are intended to be when completed.

A tube 3 connects container I with a manifold 4 having longitudinallyspaced output tubes 5, 8,

I and 8.

A three way air valve 0. having an operating solenoid I0, is connectedby a tube I3 to deliver air to the top of container I to cause pressure,as desired, on top of the liquid 2 therein. A soiu'ce of air II, orconnecting tube from same, and a separate exhaust pipe I2 to atmosphereis connected to valve 9.

A push button It is connected to arelay I4 to energize same throughoscillator controlled contacts l2 andcperatevalveltoadmitairtocontainerI to cause the rising oi liquid 2 in the tubes I8, etc. When the liquidhas risen to the point desired in said tubes an impedance change deviceI! operates as will be hereinafter described to aifect an oscillatorapparatus I6 to open contacts 82 to cause deenergization of relay I4 tothereby deenergize valve 9 and exhaust air from container I toatmosphere.

The liquid is then permitted to recede in the tubes II etc., coating theinteriorof said tubes, as it recedes, with substance capable ofrendering the tubes fluorescent when energized in the customary manner.

The details of the aforementioned parts" "and functions will now bedescribed more particularly.

The tubes l8, IBa, I8!) and I80 desired to be coated with fluorescentpowder are mounted in holders I 9, 20, 2I and 22, respectively, in whichthey may be readily inserted to be treated and thereafter removed to bereplaced by other tubes when the process of coating their interiors hasbeen completed.

The details of the mounting for the tubes I8, etc., being treated areshown more particularly in Figures 3 and 4, wherein holders I9, etc.,are

mounted upon a plate 28. Each holder I8, etc., is recessed to provide arubber gasket 28 apertured to receive the upper end of the correspondingmanifold tube such as 5, and seal the lower end of the correspondingtube to be treated, such as I8, in said holder. ii flanged and aperturedclosure 30 surrounds the lower end of the tube It and holds the gasket28 in position.

Yieldably and vertically movable top cap 28, 23a, 23b and 22c areprovided for the upper ends of the tubes I8, etc., whereby these tubesmay be readily inserted or removed from the holders I9, etc., asdesired. These caps 23, 23a, 23b and 220 are each mounted upon the lowerend of a stem or plunger 25 which extends through abearing plate 21 anda bearing 26, each plunger being provided with an integral knob III anda spring 24 holding the cap down against the top of the correspondingtube to removably hold same in its corresponding holder. The bearln8plate 27 is vertically and adjustably supported on vertical rods 32 and33 attached to and extending up from plate 28. The rods 32 and 32 extendthrough bosses or bearings 34 and 25 on opposlte ends of bearing plate21 and are provided with adjustable set screws 36 so that adjustment maybe made to accommodate tubes of different lengths.

The impedance change device II comprises a pair of metal plates 31 and38 (Fig. 2) s ared annotated to at laterally-spaced positions on thetube I8 at the a justable vertical position thereon at which it isdesired to commence the coating of the interior thereof with thesubplates.

The plates 31 and 38 are connected to a self contained grid tank unit 39for the oscillator it. This unit 39 is mounted in a suitable housing toand comprises an inductance coil M and condenser t2 and together withthe plates 31 and 38 forms a resonating circuit with said platesconnected to opposte ends of said coil and said condenser connected toone end of said coil. A pair of male plugs t3 and M are connectedrespectively to one end of coil 41! and the condenser $2.

The male plugs 43 and 4c are adapted to connect with female connectorelements 35 and 56 respectively, at one end of a concentric conductorcable 61 insulated'from ground by an external rubber sheath or cover(not shown). The cable 4! comprises an inner conductor 98, separa-' tors49 and an outer conducting sheath 50. The end of the cable opposite tothe connector 53-56 is provided with a connector Ma similar thereto forconnection to the input of an oscillator circuit l6 hereinafterdescribed.

The concentricco-axial conductor cable M is constructed in well knownmanner with its core conductor fixedly and concentrically positionedwithin the conducting sheath. By properly choosing the values of thecapacitive and inductive components of the resonating circuit inenclosure so, the cable is properly terminated so that minimum powerlosses are obtained in the system due to the cable for any substantiallength thereof. In this manner the remote control assembly Justdescribed may control the oscillator apparatus 16 hereinafter describedwithout fear of transmission losses which otherwise would reduce thesensitivity of the apparatus if not actually prevent its operation.

asoaaao ing negative or non-conducting portion of A. C.

cycle. Transformer secondary winding ll is connected to filaments 59 andH to heat cathodes 5B and I0, respectively, by wires X-X not completed.The grid bias for effectingproper operation of the repeater tube 61 isobtained by connecting the grid or control electrode 58 to one end ofthe load resistor is, the remaining portion of this circuit extendingfrom the' cathode 1o to the secondary transformer winding 16, theconductor 18a to the opposite end of the load resistor it. It will beapparent that the voltage across the winding 16 is opposite to and thuscompensates for a portion of the voltage drop across the load impedancei3 and accordingly when the oscillator tube isin oscillatory conditionso that a plate current of low value flows through the load impedance13, a minimum negative bias ,equal to the difference between the voltageof the winding 18 and the voltage drop across the load across the loadimpedance is is impressed on the grid 58. Under these conditions, andwith proper The oscillator circuit includes a vacuum tube 55 connectedto a plate tank comprising an inductance B0, variable condenser SI fortuning to resonance, as will hereinafter be described, and grid biasresistor or grid leak 12 for said tube.

Alternating current voltages are obtained from a multi-windingtransformer having a primary winding 66, connected to a suitable sourceof alternating current 65, and having a plurality of secondary windings66. i5, i8 and ii arranged to supply suitable voltages to the tubecircuits. The tube 55 and repeater tube 81, hereinafter described,"areself rectifying and therefore the operation will be described only withrespect to the positive half cycles of the alternating current voltages.

The output section of the tube 55 may be traced from the left-=handterminal of the secondary winding 65 through the plate tank circuit so,of, the anode or plate 5?, the cathode 58, thesecondary winding it,conductor its, a load impedance or resistor 13 and thence to the righthand terminal of secondary winding 68. By-pass con densers 82 and is areconnected as shown and prevent the fiow of high frequency oscillatorycurrents through the transformer windings and through the load impedanceit. 'The total voltage impressed across the anode circuit of tube '55 isthe sum of the voltages of the secondary windings 66 and I8.

voltages, the tube constants, and the value of the load resistance allso pre-chosen to provide a low negative grid bias, a high repeater platecurrent is obtained for proper operation of the relay.

A regenerative coupling is provided betweenv the grid circuit of thetube 55 and the output of the repeater tube 67, as shown. The gridcircuit for the oscillator tube 55 extends from the cathode 58, thetransformer winding 16, the lower end of relay winding it, the tap B0and the grid bias resistor or grid leak E2 to the grid 55.

A fixed grid bias is applied, by the above circuit, to the grid 56 whichis equal to the voltage drop across the relay winding is to tap 80 andis so chosen that with maximum current fiowing in the output circuit ofthe amplifier or repeater tube 6? the maximum desired negative bias isapplied to the grid 56.

The plate tank is tuned to predetermined resonance with condenser 6| soas to energize relay 18 when liquid in tube 18 is below thepredetercrease in current through the relay 19 causes adecrease in thenegative grldbias applied to the grid of the oscillator tube 55, whichtends to furrelay 19 to release air from container 1 as will 'behereinafter more particularly described."

In order to initiate a coating cycle a clean tube i8 is placed inposition as described. The oscillator circuit being in resonance becauseof the low capacity between plates 3l-38 maintains the relay contact 82closed. The push button I5 is now depressed energizing the relay itthrough I5 and B2. The armature Ma pulls down closingccnt-act 83 toenergize valve iii to allow air pressure to chamber 5. The contact 34closes to lock the relay M in closed position. The push button i5 maynow be released. As the liquid rises in it, due to air pressure inchamber I, it will eventually reach the prechosen level whereuponthecontacttt will open to deenergize locked up relay M. The contact 83will open to deenergize valve Ill releasing the air pressure in chamberi to atmosphere whereupon the liquid in tube IE will recede to leavetube coated. The contact 35 will close energizing the indicator 86 toindicate that a coating cycle has been completed. A new tube may then beplaced in the holder.

when anew and clean tube is is placed in apparatus again after removalof coated tube the oscillator circuit is retuned and oscillator .platecurrent drops, decreasing the drop across resistor 13, which decreasesthe negative bias on the amplifier tube 61; the plate current of theamplifier increases, increasing the drop across the relay 13, whichincreases the negative bias on the grid of the oscillator 55, aiding indropping the oscillator plate current, which further tends-t0 decreasethe bias upon the amplifier 61, etc., with the result that the finalpositioning of the plate current of amplifier 61 is at saturation. Bythe judicious choosing of load resistance 13, of the resistance of therelay winding 79 and the proper apportioning of bias voltages as shown,the valuesof plate current between cut-off and saturation may be fixedat any desired value. The result is that large, abrupt, and rapid platecurrent changes are always ob-' tained. The result obtainable iscomparable to the triggering off of a Thyratron type hot cathode gridcontrol rectifier without. the necesv sity of using gasfilled tubes.

Study of the circuit arrangement will also bring out that the system isself compensating for changes in line voltage which prevents shiftage ofthe control point if the line voltage should change.

It is not necessary that the apparatus be limited to the use of separatevacuum tubes, each containing separate triode elements, since theseseparate tubes have been chosen only as a matter of convenience. Dualpurpose tubes having triode elements in a common envelope may beoperated in the same manner. Direct current voltages may also be used.

It will be noted that the plate supply for tubes 55 and l! are obtainedfrom windings 86 and II, respectively, in series with 16. Should theline voltage fall the supply voltage from 15 would reduce and thereforethe plate current flow in plate circuit of tube 61 would tend todecrease. However, since winding 66 supplies the plate circuit of tube55 and since the negative bias on grid 68 is obtained from drop acrossresistor 13 due to plate current flow in plat circuit of tube 85, theplate current of tube'ii is also reduced with reduction o voltage from66. Therefore negative bias on grid .68 is reduced keeping the platecurrent flow in plate circuit of tube 61 substan' tially constant. Thereverse result is obtained with rise in line voltage. This selfcompensating feature is important in electronic control apparatus sinceit prevents shift of the control point or level upon changes in linevoltage.

Aging of tubes is also compensated for in the same manner in conjunctionwith the regenera tive connection between tap Maud resistor 12.

In summary, the advantages of this circuit are manifest, inasmuch as a.relay with a high throwout percentage is not necessary, since the platecurrent changes through said relay are very rapid and very large. It isimpossible to lose control of the oscillator, since, because of the factthat it is self-rectified, oscillations, no matter how minute, willalways reoccur. Other variaticns of this'circuit will readily occur tothose versed in the art, such as the use of a common power supply, witha self-rectified circuit, instead of separate voltages as shown. Suchcircuits have been designed and are entirely feasible. The one shownbeing one of a family of such circuits and being chosen as the mostdescriptive of the aboveexplained operation.

As shown in cross section in Figure 5, the plates 31 and 38,symbolically shown in Figure 2,. each partially circumscribes the tubei8 and are mounted upon a non-conducting portion fitia of the enclosureof Figure 2.

In the previous embodiment two capacitorplates were used with the liquidacting as a dielectric to change the capacity between said plates as inFigure 5. In Figure 7 a single plate We is used to partly circumscribetube 58 which acts as one plate of the condenser while a groundconnection at 2a in Figure 2 makes the liquid itself the other plate ofthe condenser since the liquid itself may be partly conducting.

I am aware that many changes may be made and details varied withoutdeparting from the principles of my invention and I therefore do notwish to be limited to the details shown or described.

I claim:

1. In combination, an apparatus adapted to perform an operation cyclehaving means for per forming the first part of the cycle and, uponreversal of said means, for performing the second part of the cycle, animpedance change device responsive to the operation cycle, an oscillatorcircuit adapted to have its tuning changed by said device at the end ofthe first part of the cycle and means controlled by the oscillator, uponthe change in tuning thereof, to reverse said means for performing thesecond part of the cycle of operation.

2. In combination, an apparatus adapted to 69 perform an operation cyclehaving means upon being initiated, for performing the first part of thecycle and. upon reversal of said means. for performin the second part ofthe cycle, an impedance change device responsive to the condition of thecycle, an oscillator circuit adapted to have its tuning changed by saiddevice upon the attainment of the condition of said cycle at the end ofthe first part thereof, and means controlled by the oscillator, upon thechange in tun- 70 ing thereof, for reversing the first means to causethe performance of the second part of the cycle and retuning of theoscillator, said last means including initiating means interposedbetween said oscillator and first means for initiating the letreturnedfrom again affecting the first means until the initiating means has beenoperated.

3. In combination, an apparatus for applying a substance to the interiorof tubes by the introductlon and withdrawal of a vehicle carrying thesubstance to and from the tube, means for introducing said vehicle and,upon reversal, for withdrawing the vehicle and applying the substance tothe interior of the tubes, an impedance change device responsive to theposition of the vehicle within one of the tubes, an oscillator circuitadapted to have its tuning changed by said device when said vehicle hasbeen introduced a predetermined amount into the tube and meanscontrolled by the oscillator, upon the change in tuning thereof, toreverse said means for causing the withdrawal of said vehicle and theapplication of said substance to the interior of the tubes.

4. In combination, an apparatus for applying a fluorescent substance tothe interior of tubes, means in said apparatus, upon being initiated,for introducing a vehicle into the tube carrying said substance and,upon reversal, for withdrawing from the tube and applying the substancethereto, an impedance change device responsive to the position of thevehicle within the tube, an oscillator circuit adapted to have itstuning changed by said device upon said vehicle being introduced performan operation cycle having means upon being initiated, for performing thefirst part of the cycle and, upon reversal of said means, for performingthe second part of the cycle, an impedance change device response to thecondition of the cycle, an oscillator circuit adapted to have itstuningchanged by said device upon the attainment of the condition ofsaid cycle at the end of the first part thereof, and means con-' trolledby the oscillator, upon the change in tuning thereof, for reversing thefirst means to cause the performance of the second part of the cycle andrctuning of the oscillator.

6. In combination, an apparatus for applying a substance to the interiorof tubes, means in said apparatus; upon being initiated, for introducinga vehicle into the tube carrying said substance and, upon reversal, forwithdrawing from the tube and applying the substance thereto, animpedance change device responsive to themsition of the vehicle withinthe tube, an oscillator circuit adapted to have its tuning changed bysaid device upon said vehicle being introduced a predetermined amountinto the tube and means controlled by the oscillator, upon the change intuning thereof, for reversing the first means to cause the withdrawal ofthe vehicle to apply said substance to the tube and retune'theoscillator.

'7. In combination, an apparatus adapted to perform an operation cyclehaving means for performing the first part of the cycle and, uponreversal of said means, for performing the second part of the cycle, animpedance change device responsive to the operation cycle, on oscillatorcircuit adapted to have its tuning changedbyaaiddeviceattheendotthefirstpartoifthe change device response to thecondition of the cycle and retuned during the second part of the cycle,means controlled by the oscillator, upon the tuning change thereof, toreverse said first means, and means for initiating the first means whenthe oscillator is retuned and preventing the first means from beingaffected by the retuning of the oscillator unless the initiating meansis operated.

8. In combination, an apparatus adapted to vice at the end of the onepart of the cycle and means controlled by the oscillator, upon thechange in thereof, to reverse said means for performing the other partof the cycle of operation.

9. In combination, an apparatus adapted to perform an operation cyclehaving means upon being initiated, for performing one part of the cycleand, upon reversal of said means, for per forming another part of thecycle, an impedance change device responsive tothe condition of thecycle, an oscillator circuit adapted to have its tuning changed by saiddevice upon the attainment of the condition of said cycle at the end ofone part thereof, and relay means controlled by the oscillator, upon thechange in tuning thereof, for reversing the first means to cause theperformance of the other, part of the cycle and retuning of theoscillator, a second relay and a push button therefor interposed betweensaid oscillator relay and first means for initiating the latter and forpreventing theosclllator upon being returned from again affecting thefirst means until the push button has been operated.

10. In combination, an apparatus adapted to perform an operation cyclehaving means for performing one of the cycle and, upon reversal of saidmeans, for performing another part of the cycle, an impedance changedevice responsive to theoperation cycie, an oscillator circuit adaptedto have its tuning changed by said device at the end of the one part ofthe cycle and retuned during the other part of the cycle, meanscontrolled by the oscillator, upon the change in tuning to reverse saidfirst means,

and means for initiating the first means when the oscillator is retunedand preventing the first means from being affected by the retuning ofthe oscillator unless the initiating means is operated.

11. In combination, an apparatus adapted to perform an operation cyclehaving means up being initiated, for performing one part of the cycleand, upon reversal of said means, for performing another part of thecycle, an impedance cycle, an oscillator circuit adapted to have itstuning changed by said device upon the attainment of the condition ofsaid cycle at the end of the one part thereof, and means controlled bythe oscillator, upon the change in tuning thereof, for reversing thefirst means to cause the performance of the other 'part of the cycle andretuning of the oscillator. Y

12. In combination, an apparatus adapted to perform an operation cyclehaving means upon being initiated, for performing the first part of thecycle and, upon reversal 0! said means, for performing the second partoi the cycle, an impedance chance device responsive to the condi-13,899,929 'tion of the cycle, an oscillator circuit adapted to have itstuning changed by said device upon the attainment of the condition ofsaid cycle at the end of the first part thereof, and relay meanscontrolled by the oscillator, upon the change in tuning thereof,- forreversing the first means to cause the performance of the second p rt ofthe cycle and retuning of the oscillator, a second relay and a pushbutton therefor interposed between said oscillator relay and first meansfor 'initiatingthe latter and for preventing the osvice responsive tothe operation cycle, on oscillator circuit adapted to have its tuningchanged "by said device at the end of the first part of the cycleandretuned during the second part of the cycle, relay means controlledby the oscillator,

upon the change in tuning thereof, to reverse said means and secondrelay means for initiating the first means when the oscillator isretuned and preventing the first means from being affected by theretuning of the oscillator unless the initiating means is operated.

14. In combination, an apparatus adapted to perform an operation cyclehaving means, upon being initiated, for performing one part of the cycleand, upon reversal'of said means, for performing the other part of thecycle, an impedance change device responsive to the condition of thecycle, an oscillator circuit adapted to have its tuning changed by saiddevice upon the attainment of the condition of said cycle at the end ofthe one part thereof, and means controlled by the oscillator, upon thechange in tuning thereof, for reversing the first means to cause theperformance of the other part of the cycle and retuning of theoscillator, said last means including initiating means interposedbetween said oscillator and first means for initiating the latter andfor preventing the oscillator, upon being retuned, from again affectingthe first means until the initiating means has been operated.

15. In combination, an apparatus adapted to Perform an operation cyclehaving means for performing one part of the cycle and, upon reversal ofsaid means, for performing another part of .the cycle, an impedancechange device responsive to the operation cycle, an oscillator circuitadapted to have its tuning changed by said device at the end of the onepart of the cycle and retuned during the other part of the cycle, relaymeans controlled by the oscillator, upon the change in tuning thereof,.to reverse said means. and second relay means for initiating the firstmeans when the oscillator is retuned and preventing the first means frombeing aflected bythe retuning of the oscillator unless the initiatingmeans is operated.

1 6. In combination, an apparatus adapted to .perform an operation cycleupon a physical medium and having means for performing the first part ofthe cycle and, upon reversal of said means, for performing the secondpart of the cycle, an impedance change device responsive to the op-.eration cycle and situated in proximity to a predetermined point withrespect to said medium, an oscillator circuit adapted to have its tuningond Part of the cycle, an impedance change depart of the cycle and meanscontrolled by the oscillator, upon the change in tuning thereof, toreverse said means for performing the second part of the cycle ofoperation, said means acting to perform the first part of the cycle froma predetermined starting point with respect to said medium spaced fromthe predetermined point in proximity to said device and, upon reversal,to perform the second part of the cycle from the last mentioned pointback to said starting point. 1

17. In combination, an apparatus adapted to perform an operation cycleupon a physical medium and having means for performing the first part ofthe cycle and, upon reversal of said means, for performing the secondpart of the cycle, a pair of capacitor plates and an oscillating circuitresponsive to'the operation cycle and situated in proximity to apredetermined point with respect to said medium, an oscillator circuitadapted to have its tuning changed by said plates and connected to saidfirst circuit and means controlled by the oscillator, upon change intuning thereof, to reverse said means for performing the second part ofthe cycle of operation, said means acting to perform the first part ofthe cycle from a predetermined starting point with respect to saidmedium spacedfrom the predetermined point in proximity to said platesand to perform the second part of the cycle from said last point back tosaid starting point. I

18. In combination, an apparatus adapted to perform an operation cycleupon a physical medium and having means. for performing the first partof the cycle .and, upon reversal of said means,

for performing the secondpart of the cycle, a pair of capacitor platesand situated inproximity to a predetermined point with respect to saidmedium and an oscillating circuit, an oscillator circuit tuned topredetermined resonance with and including said oscillating circuit, aconcentric from the predetermined point in proximity to said plates andto perform the second part of the cycle from said last mentioned pointback, upon reversal, to said starting point.

' 19. In combination, an apparatus adapted to perform an operationcycleupon a physical medium and having means for performing the first part ofthe cycle and, upon reversal of said means, for performing the secondpart of the cycle, an impedance change device responsive to theoperation cycle and situated in proximity to a predetermined point withrespect to said medium.

an electronic circuit adapted to be operated at the end of the firstpart of the cycle by said 'device and means controlled by said circuit,upon the operation thereof, to reverse said first means for performingthe second part of the cycle of operation, said means acting to performthe first part of the cycle from a predetermined startin point withrespect to said medium spaced from the predetermined point in proximityto said device and to perform the second part of the cycle from saidlast mentioned point back to said startin point.

changed by said device at the end' of the first 7 20. In combination, anapparatus adapted to perform an operation cycle upon a physical mediumand having a valve, a pneumatic means controlled thereby for performingthe first part of the cycle, and, upon reversal of said valve, forperforming the second part of the cycle, an impedance change deviceresponsive to the operation cycle and situated in proximity to apredetermined point with respect to said medium, an oscillator circuitadapted to have its tuning changed by said levice at the end of thefirst part of the cycle and means controlled by the oscillator, upon thechange in tuning thereof, to reverse said valve for performing thesecond part .of the cycle oi! operation, said pneumatic means acting toperform the first part of the cycle from a predetermined starting pointwith respect to said medium spaced from the predetermined point inproximity to said device and, upon reversal, to perform the second partof the cycle from said last mentioned point back to said starting point.

21. In combination, an apparatus adapted to perform an operation cyclehaving means for performing the first part of the cycle and, uponreversal of said means,. for performing the secstarting point to theattainment of said level and from the lowering of said level back tosaid starting point.

22. In combination, an apparatus for applying a substance to theinterior of tubes by the introduction and withdrawal of a vehiclecarrying the substance to and from the tubes, means for introducing saidvehicle and, upon reversal, for withdrawing the vehicle and applying thesubstance to the interior of the tubes, an impedance change deviceresponsive to the position of the vehicle within one of the tubes, anoscillator circuit adapted to have its tuning changed by said devicewhen said vehicle has been introduced a predetermined amount into thetube and means controlled by the oscillator, upon the change in tuningthereof, to reverse said means for causin the withdrawal of said vehicleand the application of said substance to the interior of the .tubes, anda stand for said tubes provided with a plurality of supports for thelower ends of tubes and a plurality of yieldably held caps for the upperends of said tubes.

23. In'combination, an apparatus for applying a substance to tubes byapplying a vehicle carrying the substance longitudinally to the tube,means for moving the vehicle longitudinally of the tube and, uponreversal, for moving said vehicle in the other direction, an impedancechange device responsive to the position of the vehicle with respect tothe tubes, an oscillator circuit adapted to have its tuning changed bysaid device when said vehicle has attained a predetermined position withrespect to the tube, and means controlled by the oscillator, upon achange in tuning thereof, to reverse said means for causing the oppositemovement of said vehicle.

mononn A. COHEN.

